In this section we gauge the \(\mathsf {Out}(G)\) -symmetry of two-dimensional Yang-Mills theory
using the generalised orbifold construction
[1]}, [2]}, [3]}, [4]}
of a functorial defect quantum field theory.
We start by recalling the notion of area-dependent quantum field theories and their state sum constructions in
Section REF . Then we give a detailed description of the
bicategory of topological defects of two-dimensional Yang-Mills theories in Section REF , and in Section REF  we discuss the regularised Frobenius algebras constructed from a Lie group and its outer automorphism group.
Finally, in Section REF  we gauge the
\(\mathsf {Out}(G)\) -symmetry, and using an orbifold equivalence in the orbifold
completion of the topological defect bicategory we give the defect for the reverse orbifold in Section REF .
